Spray gun



March 13, 1962 R. MAURATH 5 SPRAY GUN Filed April 10, 1961 J L 2s 2 29 3 l5 48 36 i 31 I I I g I I H? I! j 1 hill" 39 I' 5 I l 4| 4 Ii 34 FIGZ *fin 42 u 3 El -Emit 33 I I] H INVENTOR.

FIG. 3- RAYMOND L. MAURATH AT TOR NEY United fitates Patent 3,025,006 Patented Mar. 13;, 1962 sonri Filed Apr. 10, 1961, Ser. No. 101,863 6 (Ilaims. (Cl. 239-424) This invention relates in general to certain new and useful improvements in coating equipment and, more particularly, to spraying apparatus for use in the application of highly viscous coarse-aggregate material.

At the present time, there are a number of coating materials which embody a high loading of very coarse aggregate, such as sand, expanded vermiculite and the like. For instance, there are Wall paints which are commonly used to simulate a so-called sand'plaster effect. Some types of acoustical ceilings are made by applying a relatively thick coating of coarse-aggregate material which is very porous or spongy. Such materials are quite commonly brushed or troweled upon a surface by hand or applied by so-called Gunite equipment. These existing methods of application, however, are not particularly satisfactory for a number of reasons.

Hand methods of application, such as brushing or trowcling, are slow, time-consuming and comparatively costly in terms of labor. Moreover, heavily loaded materials when brushed or troweled upon a vertical surface must be dealt with very carefully otherwise the coating will run and sag. In addition to this, it is necessary to stir the coating material almost constantly otherwise there is a tendency for the aggregate to settle and the density of the coating material will change very markedly as it is brushed or troweled upon successive areas of the surface. Another difiiculty which is encountered in brushing or troweling such materials upon surfaces is the tendency to work the fluid material as it is being applied and, in effect, compress the film in the case of so-called sand-finishes. This results in a noticeable tendency to pull the aggregate together, so that in some areas of the film there will be an excessive distribution of the aggregate whereas in other areas of the film the aggregate will be sparsely distributed, thereby producing an irregular or non-uniform appearance upon the finished surface. In the case of acoustical coatings, the compaction of the coating material of course reduces the sponginess of the finished coating and this, in turn, reduces the efficiency of the coating as a sound-absorption medium.

Similar disadvantages are encountered by the use of so-called Gunite equipment in which the liquid coating material is forced through a large diameter pipe or tube by a stream of high-pressure air which is blown forcibly against the surface which is being coated. Not only does the high-pressure stream produce stratification and striation of the coarse-aggregate material, but, also, requires a great deal of skill on the part of the operator, and even where the operator is most skillful, the splashing of materials onto adjacent surfaces is extremely pronounced. In fact, Gunite equipment produces so much splashing, splattering and over-spray that it is impossible to protect furniture, carpeting, floor-surfaces and the like in an ordinary room by the use of drop cloths and conventional masking techniques. Moreover, in the case of acoustical treatment, Gunite equipment produces a high degree of compaction and the resulting coating is far less efiicient as a sound-absorption medium than it ordinarily should be.

It is, therefore, the primary object of the present invention to provide apparatus which is capable of applying coating materials having a high loading of sand or other similar coarse-aggregates rapidly, efficiently and economically.

It is another object of the present invention to provide apparatus of the type stated which is capable of applying high viscosity coatings to both horizontal and vertical surfaces in a smooth even-density film.

It is a further object of the present invention to provide apparatus of the type stated which is capable of handling high viscosity coating materials which are loaded or pigmented with coarse materials having a relatively large average particle size.

It is an additional object of the present invention to provide apparatus of the type stated which will form a finely divided or highly atomized film-forming spray from high viscosity coarse-aggregate coating materials at relatively low air pressure.

It is a further object of the present invention to provide apparatus of the type stated which will apply high viscosity coarse-aggregate film-forming materials to surfaces with a minimum of bounce-back and over-spray.

It is also an object of the present invention to provide apparatus of the type stated which is capable of spraying coatings upon surfaces in a smooth, uniform film without either excessive air entrapment, on the one hand, or undue compaction of the coating, on the other.

It is an additional object of the present invention to provide apparatus of the type stated which is capable of applying coating films to surfaces in a uniform manner such that the thickness of the film is not only uniform but may also be precisely controlled.

It is a further object of the present invention to pro vide apparatus of the type stated which may be easily disassembled and cleaned with a minimum amount of lost time or effort and is, therefore, particularly adapted for handling coating materials with a so-called short pot-life.

With the above and other objects in view, my invention resides in the novel features of form, construction, arrangement, and combination of parts presently described and pointed out in the claims.

In the accompanying drawing (one sheet):

FIG. 1 is a diagrammatic view, partly broken away and in section, of spraying apparatus constructed in accordance with and embodying the present invention;

FIG. 2 is a fragmentary sectional view taken along line 22 of FIG. 1; and

FIG. 3 is a fragmentary sectional view taken along line 3-3 of FIG. 2.

Referring now in more detail and by reference characters to the drawing, which illustrates a preferred embodiment of the present invention, A designates a liquidmaterial reservoir comprising a relatively heavy gauge deep-drawn tank 1 having a downwardly curved bottom wall 2. Welded at suitably spaced intervals around the outer face of the tank 1 adjacent to the bottom wall 2 are downwardly extending legs 3 which are rigidly secured at their lower ends to a horizontal frame or platform 4, which is preferably of rectilinear shape and is provided at its four corners with casters 5.

At its upper end, the tank 1 is provided with a smoothly machined horizontal top margin 6 which seats against the under side of a gasket 7 mounted in the downwardly presented annular shoulder 8 of a cover or top-closure 9 which extends across the top of the tank 1 and is integrally provided with a depending annular skirt or flange 10 which encircles the upper exterior face of the tank 1. Welded or otherwise rigidly secured to, and projecting radially outwardly from, the external face of the tank 1 in downwardly spaced relation to the lower peripheral margin of the skirt 1:; are suitably spaced pairs of ears 1?. for supporting horizontal pins 12, which, in turn, rock-ably support the lower ends of clamping screws 13, which are, in turn, adapted to swing upwardly between registering pairs of cars 14 for clamping securement by means of wing-nuts 15. It will, of course, be apparent that by tightening down uniformly on the several wing-nuts it is possible to draw the top-closure or cover 9 down securely into pressure-tight engagement across the top of the tank 1. Welded or otherwise rigidly secured upon the top face of the cover 9 and projecting vertically upwardly therefrom are legs 16, 17, which are rigidly secured at their upper ends to an electric motor 18 having a downwardly projecting vertical drive shaft 19 which is connected to a conventional shaft-coupling 20 to an agitator shaft 21, the latter being operativel y disposed through a conventional rotary seal and bearing assembly 22. At its lower end, the agitator shaft 21 extends downwardly into the interior of the tank 1, terminating a short distance above the bottom wall 2 and being rigidly provided on such lower extremity with an agitator blade 23. The electric motor 18 is conventionally provided with an electric connector cord for connection to a suitable source of electric power (not shown).

Threadedly seated in and extending through the cover 9 is a vertical nipple 24 which is provided on its upper end with a conventional manually operable pressure release valve L and similarly seated in the cover 9 is another airinlet nipple 25 which is provided at its upper end with a conventional T-fitting 26 and pressure-gauge 27. The T- fitting 26 is also connected to a conventional pressurereducing valve 28, which is, in turn, connected by a suitable pipe or conduit 29 to a conventional source of compressed air (not shown). Threadedly mounted in and extending centrally through the bottom wall 2 for communication with the interior of the tank 1 is a discharge pipe 30 having a T-fitting 31 which accommodates a laterally extending pressure-gauge 32.

Secured upon the lower end of the T-fitting 3-1 is a flexible tube or hose H which may be of any desired or convenient length and is similarly connected at its remote end by means of a conventional hose clamp 33 to the lower end of an intake tube 34 forming part of a spray nozzle B comprising a cylindrical shell 35 having a fiat circular back wall 36 and forming a chamber c into which the intake tube 34 opens. Welded or otherwise rigidly secured upon the back wall 36 and extending concentrically and forwardly therefrom is a sleeve 37, the interior bore of which registers with an aperture 38 formedcentrally in the back wall 36. Welded upon the external face of the back wall 36 in overlying relation to the aperture 38 and extending radially downwardly therefrom in more or less parallel relation to the intake tube 34 is an air-supply fitting 39 provided at its lower end with an externally threaded nipple-portion 40, which is, in turn, connected by means of a conventional tuhe coupling 41 to a compressed air line 42, which is, in turn, conventionally connected to a source of compressed air (not shown). The air-supply fitting 39 is internally provided with a bore 43 which extends vertically through the airsupply fitting 39 and terminates at the upper end thereof in an internal air-supply chamber Threadedly mounted in and extending transversely through the lower portion of the air-supply fitting 39 is a needle valve-45 which extends across the bore 43 and may be threaded in or out to control the air flow into the air-supply chamber c At its outer end, the needle valve 45 is conventionally provided with a diametrally enlarged knurled knob 46 to facilitate manual adjustment thereof. Also threadedly mounted in and extending through the upper end of the air-supply fitting 39 is a nozzle-tube 47 integrally provided on its external end with a diametrally enlarged knurled knob 48 and having a diametral size for snugfitting sliding and rotative fit through the aperture 38 and the internal bore of the sleeve 37. The nozzle-tube 47 is internally provided with a bore 49 which extends toward the rear end ofthe nozzle-tube 47 and terminates within that portion of the nozzle-tube 47 that is located within the chamber c In this rear portion, which is located within the chamber 0 the nozzle-tube 47 is provided with a pair of diametrally opposed apertures or ports 50, 51, through which air under pressure may flow from the chamber c into the bore 49 and out through the forward end of the nozzle-tube 47. At its forward end, the nozzle-tube 47 is externally threaded for receiving an internally threaded nozzle-tip 52 having an air discharge aperture 53 of relatively small diametral size. Preferably, this aperture 53 has a diametral size of the order of .05 inch to .075 inch.

At its forward end, the shell 35 is externally threaded for receiving an internally threaded cap-plate 54 of outwardly convex contour. Rigidly seated in and extending coaxially through the cap-plate 54 is an internally threaded collar 55, and threaded thereinto is a discharge nozzle 56 having an internal bore or nozzle-passage 57 which is co-axial with and substantially larger than the air discharge aperture 53.

It will be noted by reference to FIG. 3 that the nozzletube 47 is of such length that it will extend through the chamber 0 and terminate in rearwardly spaced relation to the rear end of the discharge nozzle 56. By rotating the nozzle 56, it can be threaded forwarded or rearwardly to adjust the distance or gap between the air discharge aperture 53 and the rear end of the nozzle tube 56 in order to control the velocity and quantity of liquid material being discharged and also to regulate the degree of atomization thereof.

In use, the cover 9 may be removed and lifted off of the top of the tank 1 and a suitable quantity of viscous coarse.- aggregate coating material in liquid form may be poured into the tank 1. Thereupon, the cover 9 may be lowered down upon the tank 1 and as this is done the agitator blade 23 will be correspondingly lowered into the body of liquid material within the tank 1. The clamping screws 13 may then be swung up between the pairs of cars 14 and the cover 9 securely clamped down in place by appropriate tightening of the wing-nuts 15. The pressurereducing valve 28 is then opened up to allow high-pressure air to flow into the tank 1 and build up pressure therein as indicated by the pressure-gauge 26. It has been found that the optimum pressure which should be maintained within the tank 1 ranges between 30-40 t.s.i. and the reducing valve 28 should be adjusted to maintain this range of air pressure within the tank 1.

In preparation for charging up the tank 1, the nozzletube 47 of the spray head B is threaded forwardly until it is actually seated against the rear end of the dischargenozzle 56, thereby acting as a closure valve. Consequently, as the air pressure builds up within the tank 1, the liquid coating material will flow downwardly into and through the hose 32 until the air, which is entrapped within the chamber 0 builds up to an equivalent pressure.

During this part of the procedure, the needle-valve 45 will be threaded tightly down into fully closed position so that no air pressure will build up in the air-supply chamber c While air pressure is building up within the tank 1, the motor 18 will be energized so that the agitator shaft 21 and agitator blade 23 will be rotated, thereby keeping the liquid coating material within the tank 1 uniformly mixed at all times. As soon as the tank 1 reaches desired operating pressure, the spray head may be pointed in the direction of, and held at a distance of approximately twelve to sixteen inches from, the surface to be coated. Thereupon, the needle valve 45 may be threaded outwardly several turns to allow air pressure to flow into the chamber c and thence through the ports 50, 51, into the bore 49 of the nozzle-tube 47. The nozzle-tube 47 is then threaded rearwardly to allow the entrapped air under pressure to flow outwardly from the chamber c As this occurs, the liquid coating material will up the hose H, filling the chamber c and flowing thence outwardly through the gap between the forward end of the nozzle-tube 47 and the rear end of the discharge nozzle 56. As the liquid coating material flows into the bore 57 of the discharge nozzle 56, it will be propelled forwardly by the air stream discharging from the aperture 53 and will be finely dispersed or atomized thereby, with the result that such liquid coating material will issue forwardly out of the forward end of the discharge nozzle 56 as a finely divided uniform spray which will deposit uniformly upon the surface being coated. By reason of the fact that the spray is thoroughly atomized, and is projected upon the surface at comparatively low pressure, there is very little bounce-back or over-spray and it is possible to control the thickness and character of the film being formed. The velocity and degree of atomization of the spray can also be very precisely controlled by appropriate adjustment of the nozzle-tube 47 and the needle valve 45, as indicated on the pressure-gauge 27. Thereupon, the clamping screws 13 may be released and the cover 9, together with the agitator shaft 21 and agitator blade 23, lifted from the tank 1 and set into a suitable large tub or container of solvent, so that all of the liquid-covered surfaces can be easily and conveniently washed off. Similarly, the spray head B can be disconnected from the hose H and the air-supply line 42. Thereupon, the cap-plate 54 can be removed and the spray head B, which is now in two parts, can be dropped into a suitable bucket or container of solvent and washed clean. The hose clamp 31 can also be disconnected so that the hose H can be coiled up and dropped into the solvent and thereby washed out. Finally, the interior of the tank 1 can be Washed out and wiped clean. Such clean-up operations are more or less conventional, but the important factor is that the apparatus of the present invention can be very quickly and simply disassembled so that such clean-up operations cam be performed with maximum speed and convenience.

In connection with the present invention, it should be noted that the nozzle-tip 52 and the discharge nozzle 56 should be fabricated of a very hard abrasion-resistant alloy-steel or, preferably, from sintered tungsten carbide so as to provide maximum life notwithstanding the highly abrasive character of the liquid coating materials flowing therethrough. Moreover, since both the nozzle-tip 52 and discharge nozzle 56 can be removed and replaced, the ultimate wearing out of these parts does not constitute a major problem.

It should be understood that changes and modifications in the form, construction, arrangement, and combination of the several parts of the coating equipment may be made and substituted for those herein shown and described without departing from the nature and principle of my invention.

Having thus described my invention, what I claim and desire by secure by Letters Patent is:

l. A spray-gun for spraying a heavily-loaded coating material, said spray-gun comprising an outer shell with an internal chamber having a discharge nozzle, means for supplying the coating material under pressure to said chamber so that it will flow in a stream through the discharge nozzle, an air-pressure supply element mounted on said shell and having a vertical bore that terminates at its upper end in a second chamber, and a nozzle tube mounted in the second chamber of said air pressure supply element, said nozzle tube being provided with a pair of opposed apertures in the portion located in the second chamber extending into said internal chamber, said nozzle tube having an orifice located adjacent to the interior end of the discharge nozzle for atomizing the stream of coating material flowing through the discharge nozzle.

2. A spray-gun for spraying a heavily-loaded coating material, said spray-gum comprising an outer shell with an internal chamber having a discharge nozzle, means for supplying the coating material under pressure to said chamber so that it will flow in a stream through the discharge nozzle, an air-presure supply element mounted on said shell and having a vertical bore that terminates at its upper end in a second chamber, a nozzle tube mounted in the second chamber of said air pressure supply element, said nozzle tube being provided with a pair of opposed apertures in the portion located in the second chamber extending into said internal chamber, said nozzle tube having an orifice located adjacent to the interior end of the discharge nozzle for atomizing the stream of coating material flowing through the dicharge nozzle, and valve means for throttling the air flowing through the air-pressure supply element.

3. A spray-gun for spraying a heavily-loaded coating material, said spray-gun comprising an outer shell with an internal chamber having a discharge nozzle, means for supplying the coating material under pressure to said chamber so that it will flow in a stream through the discharge nozzle, an air-pressure supply element mounted on said shell and having a vertical bore that terminates at its upper end in a second chamber, a nozzle tube mounted in the second chamber of said air pressure supply element, said nozzle tube being provided with a pair of opposed apertures in the portion located in the second chamber extending in to said internal chamber, said nozzle tube having an orifice located adjacent to the interior end of the discharge nozzle for atomizing the stream of coating material flowing through the discharge nozzle, and means for adjusting said element within the chamber to vary the distance between said orifice and the interior end of said discharge nozzle.

4. A spray-gun for spraying a heavily-loaded coating material, said spray-gun comprising an outer shell with an internal chamber having a discharge nozzle, means for supplying the coating material under pressure to said chamber so that it will flow in a stream through the discharge nozzle, an air-pressure supply element mounted on said shell and having a vertical bore that terminates at its upper end in a second chamber, a nozzle tube mounted in the second chamber of said air pressure supply element, said nozzle tube being provided with a pair of op posed apertures in the portion located in the second chamber extending into said internal chamber, said nozzle tube having an orifice located adjacent to the interior end of the discharge nozzle for atomizing the stream of coating material flowing through the discharge nozzle, valve means for throttling the air flowing through the air-pressure supply element, and means for adjusting said element within the chamber to vary the distance between said orifice and the interior end of said discharge nozzle.

5. A spray-gun for spraying a heavily-loaded coating material, said spray-gun comprising an outer shell with an internal chamber having a discharge nozzle formed of abrasion-resistant material, means for supplying the coating material under pressure to said chamber so that it will flow in a stream through the discharge nozzle, an airpressure supply element mounted on said shell and having a vertical bore that terminates at its upper end in a second chamber, and a nozzle tube mounted in the second chamber of said air pressure supply element, said nozzle tube being provided with a pair of opposed apertures in the portion located in the second chamber extending into said internal chamber, said nozzle tube having an orifice located adjacent to the interior end of the discharge nozzle for atomizing the stream of coating material flowing through the discharge nozzle.

6. A spray-gun for spraying a heavily-loaded coating material, said spray-gun comprising an outer shell with an internal chamber having a discharge nozzle formed of abrasion-resistant material, means for supplying the coating material under pressure to said chamber so that it Will flow in a stream through the discharge nozzle, an air-pressure supply element mounted on said shell and having a vertical bore that terminates at its upper end in a second chamber, and a nozzle tube mounted in the second chamber of said air pressure supply element, said nozzle tube being provided with a pair of opposed apertures in the portion located in the second chamber extending into said internal chamber, said nozzle tube having an orifice located adjacent to the interior end of the discharge nozzle for atomizing the stream of coating material flowing through the discharge nozzle, said orifice being formed of abrasion-resistant material.

References Cited in the file of this patent UNITED STATES PATENTS 1,566,325 Hansen Dec. 22, 1925 FOREIGN PATENTS Italy Aug; 16, 1929 

